diff --git a/fuzzers/011-ffconfig/top.py b/fuzzers/011-ffconfig/top.py
index 9f78e0b0..f3a5a06e 100644
--- a/fuzzers/011-ffconfig/top.py
+++ b/fuzzers/011-ffconfig/top.py
@@ -9,7 +9,7 @@ def slice_xy():
     '''Return (X1, X2), (Y1, Y2) from XRAY_ROI, exclusive end (for xrange)'''
     # SLICE_X12Y100:SLICE_X27Y149
     # Note XRAY_ROI_GRID_* is something else
-    m = re.match(r'SLICE_X(.*)Y(.*):SLICE_X(.*)Y(.*)', os.getenv('XRAY_ROI'))
+    m = re.match(r'SLICE_X([0-9]*)Y([0-9]*):SLICE_X([0-9]*)Y([0-9]*)', os.getenv('XRAY_ROI'))
     ms = [int(m.group(i + 1)) for i in range(4)]
     return ((ms[0], ms[2] + 1), (ms[1], ms[3] + 1))
 
diff --git a/fuzzers/012-clbn5ffmux/top.py b/fuzzers/012-clbn5ffmux/top.py
index e1032bad..a712fda5 100644
--- a/fuzzers/012-clbn5ffmux/top.py
+++ b/fuzzers/012-clbn5ffmux/top.py
@@ -7,7 +7,7 @@ def slice_xy():
     '''Return (X1, X2), (Y1, Y2) from XRAY_ROI, exclusive end (for xrange)'''
     # SLICE_X12Y100:SLICE_X27Y149
     # Note XRAY_ROI_GRID_* is something else
-    m = re.match(r'SLICE_X(.*)Y(.*):SLICE_X(.*)Y(.*)', os.getenv('XRAY_ROI'))
+    m = re.match(r'SLICE_X([0-9]*)Y([0-9]*):SLICE_X([0-9]*)Y([0-9]*)', os.getenv('XRAY_ROI'))
     ms = [int(m.group(i + 1)) for i in range(4)]
     return ((ms[0], ms[2] + 1), (ms[1], ms[3] + 1))
 
diff --git a/fuzzers/013-clbncy0/top.py b/fuzzers/013-clbncy0/top.py
index fa307753..254e9461 100644
--- a/fuzzers/013-clbncy0/top.py
+++ b/fuzzers/013-clbncy0/top.py
@@ -7,7 +7,7 @@ def slice_xy():
     '''Return (X1, X2), (Y1, Y2) from XRAY_ROI, exclusive end (for xrange)'''
     # SLICE_X12Y100:SLICE_X27Y149
     # Note XRAY_ROI_GRID_* is something else
-    m = re.match(r'SLICE_X(.*)Y(.*):SLICE_X(.*)Y(.*)', os.getenv('XRAY_ROI'))
+    m = re.match(r'SLICE_X([0-9]*)Y([0-9]*):SLICE_X([0-9]*)Y([0-9]*)', os.getenv('XRAY_ROI'))
     ms = [int(m.group(i + 1)) for i in range(4)]
     return ((ms[0], ms[2] + 1), (ms[1], ms[3] + 1))
 
diff --git a/fuzzers/014-ffsrcemux/top.py b/fuzzers/014-ffsrcemux/top.py
index a76897be..d87dc6ce 100644
--- a/fuzzers/014-ffsrcemux/top.py
+++ b/fuzzers/014-ffsrcemux/top.py
@@ -7,7 +7,7 @@ def slice_xy():
     '''Return (X1, X2), (Y1, Y2) from XRAY_ROI, exclusive end (for xrange)'''
     # SLICE_X12Y100:SLICE_X27Y149
     # Note XRAY_ROI_GRID_* is something else
-    m = re.match(r'SLICE_X(.*)Y(.*):SLICE_X(.*)Y(.*)', os.getenv('XRAY_ROI'))
+    m = re.match(r'SLICE_X([0-9]*)Y([0-9]*):SLICE_X([0-9]*)Y([0-9]*)', os.getenv('XRAY_ROI'))
     ms = [int(m.group(i + 1)) for i in range(4)]
     return ((ms[0], ms[2] + 1), (ms[1], ms[3] + 1))
 
diff --git a/fuzzers/015-clbnffmux/top.py b/fuzzers/015-clbnffmux/top.py
index 1d0e19e0..abd0ef97 100644
--- a/fuzzers/015-clbnffmux/top.py
+++ b/fuzzers/015-clbnffmux/top.py
@@ -7,7 +7,7 @@ def slice_xy():
     '''Return (X1, X2), (Y1, Y2) from XRAY_ROI, exclusive end (for xrange)'''
     # SLICE_X12Y100:SLICE_X27Y149
     # Note XRAY_ROI_GRID_* is something else
-    m = re.match(r'SLICE_X(.*)Y(.*):SLICE_X(.*)Y(.*)', os.getenv('XRAY_ROI'))
+    m = re.match(r'SLICE_X([0-9]*)Y([0-9]*):SLICE_X([0-9]*)Y([0-9]*)', os.getenv('XRAY_ROI'))
     ms = [int(m.group(i + 1)) for i in range(4)]
     return ((ms[0], ms[2] + 1), (ms[1], ms[3] + 1))
 
diff --git a/fuzzers/016-clbnoutmux/top.py b/fuzzers/016-clbnoutmux/top.py
index 2b34e385..11c3043c 100644
--- a/fuzzers/016-clbnoutmux/top.py
+++ b/fuzzers/016-clbnoutmux/top.py
@@ -7,7 +7,7 @@ def slice_xy():
     '''Return (X1, X2), (Y1, Y2) from XRAY_ROI, exclusive end (for xrange)'''
     # SLICE_X12Y100:SLICE_X27Y149
     # Note XRAY_ROI_GRID_* is something else
-    m = re.match(r'SLICE_X(.*)Y(.*):SLICE_X(.*)Y(.*)', os.getenv('XRAY_ROI'))
+    m = re.match(r'SLICE_X([0-9]*)Y([0-9]*):SLICE_X([0-9]*)Y([0-9]*)', os.getenv('XRAY_ROI'))
     ms = [int(m.group(i + 1)) for i in range(4)]
     return ((ms[0], ms[2] + 1), (ms[1], ms[3] + 1))
 
diff --git a/fuzzers/017-clbprecyinit/top.py b/fuzzers/017-clbprecyinit/top.py
index 0bef994c..0b7abeb8 100644
--- a/fuzzers/017-clbprecyinit/top.py
+++ b/fuzzers/017-clbprecyinit/top.py
@@ -7,7 +7,7 @@ def slice_xy():
     '''Return (X1, X2), (Y1, Y2) from XRAY_ROI, exclusive end (for xrange)'''
     # SLICE_X12Y100:SLICE_X27Y149
     # Note XRAY_ROI_GRID_* is something else
-    m = re.match(r'SLICE_X(.*)Y(.*):SLICE_X(.*)Y(.*)', os.getenv('XRAY_ROI'))
+    m = re.match(r'SLICE_X([0-9]*)Y([0-9]*):SLICE_X([0-9]*)Y([0-9]*)', os.getenv('XRAY_ROI'))
     ms = [int(m.group(i + 1)) for i in range(4)]
     return ((ms[0], ms[2] + 1), (ms[1], ms[3] + 1))
 
diff --git a/fuzzers/018-clbram/top.py b/fuzzers/018-clbram/top.py
index 84a6fd40..f1864364 100644
--- a/fuzzers/018-clbram/top.py
+++ b/fuzzers/018-clbram/top.py
@@ -24,7 +24,7 @@ def slice_xy():
     '''Return (X1, X2), (Y1, Y2) from XRAY_ROI, exclusive end (for xrange)'''
     # SLICE_X12Y100:SLICE_X27Y149
     # Note XRAY_ROI_GRID_* is something else
-    m = re.match(r'SLICE_X(.*)Y(.*):SLICE_X(.*)Y(.*)', os.getenv('XRAY_ROI'))
+    m = re.match(r'SLICE_X([0-9]*)Y([0-9]*):SLICE_X([0-9]*)Y([0-9]*)', os.getenv('XRAY_ROI'))
     ms = [int(m.group(i + 1)) for i in range(4)]
     return ((ms[0], ms[2] + 1), (ms[1], ms[3] + 1))
 
diff --git a/fuzzers/019_ndi1mux/top.py b/fuzzers/019_ndi1mux/top.py
index ea137279..d50c4067 100644
--- a/fuzzers/019_ndi1mux/top.py
+++ b/fuzzers/019_ndi1mux/top.py
@@ -7,7 +7,7 @@ def slice_xy():
     '''Return (X1, X2), (Y1, Y2) from XRAY_ROI, exclusive end (for xrange)'''
     # SLICE_X12Y100:SLICE_X27Y149
     # Note XRAY_ROI_GRID_* is something else
-    m = re.match(r'SLICE_X(.*)Y(.*):SLICE_X(.*)Y(.*)', os.getenv('XRAY_ROI'))
+    m = re.match(r'SLICE_X([0-9]*)Y([0-9]*):SLICE_X([0-9]*)Y([0-9]*)', os.getenv('XRAY_ROI'))
     ms = [int(m.group(i + 1)) for i in range(4)]
     return ((ms[0], ms[2] + 1), (ms[1], ms[3] + 1))